Thou shalt not bow down thyself to them, nor serve them: for I the LORD thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me.

Colō and excolō can be confused in usage. Deriving from the IE root Proto-Indo-European*kʷel-, colō probably had an original sense of turning (plowing for cultivation) the soil, and by extension of inhabiting a place; by further extension, it adopted the senses of improving said habitation by tilling/cultivating the land and through the specific nurture of crops. While the figurative senses of nurturing and improving are attributable to colō, they are more properly rendered by excolō, since nurture and improvement are the parts of the (literal) process of land cultivation "out of" (ex-) which springs excolō, which then renders the figurative and universal sense of tending, nurturing, improving, perfecting, and (in the figurative sense only) cultivating. Colō, cultus and cultiō, then, properly render the senses of tilling/cultivation/tending/nurture/improvement strictly in the agricultural sense, while excolō, excultus, and excultiō properly render the senses of nurture/improvement/perfection, and so improvement by means of effort, labor or study/devotion of one's attention to, all in the general, figurative, non-agricultural sense.